zram: fix incorrect stat with failed_reads

Since we allocate a temporary buffer in zram_bvec_read to handle partial
page operations in commit 924bd88d703e ("Staging: zram: allow partial
page operations"), our ->failed_reads value may be incorrect as we do
not increase its value when failing to allocate the temporary buffer.

Let's fix this issue and correct the annotation of failed_reads.

Signed-off-by: Chao Yu <chao2.yu@samsung.com>
Acked-by: Minchan Kim <minchan@kernel.org>
Cc: Nitin Gupta <ngupta@vflare.org>
Acked-by: Jerome Marchand <jmarchan@redhat.com>
Acked-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 8 insertions, 4 deletions

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index dfa4024c448a..d00831c3d731 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -378,7 +378,6 @@ static int zram_decompress_page(struct zram *zram, char *mem, u32 index)
         /* Should NEVER happen. Return bio error if it does. */
         if (unlikely(ret)) {
                 pr_err("Decompression failed! err=%d, page=%u\n", ret, index);
-                atomic64_inc(&zram->stats.failed_reads);
                 return ret;
         }
 
@@ -547,8 +546,6 @@ out:
                 zcomp_strm_release(zram->comp, zstrm);
         if (is_partial_io(bvec))
                 kfree(uncmem);
-        if (ret)
-                atomic64_inc(&zram->stats.failed_writes);
         return ret;
 }
 
@@ -566,6 +563,13 @@ static int zram_bvec_rw(struct zram *zram, struct bio_vec *bvec, u32 index,
                 ret = zram_bvec_write(zram, bvec, index, offset);
         }
 
+        if (unlikely(ret)) {
+                if (rw == READ)
+                        atomic64_inc(&zram->stats.failed_reads);
+                else
+                        atomic64_inc(&zram->stats.failed_writes);
+        }
+
         return ret;
 }
 
diff --git a/drivers/block/zram/zram_drv.h b/drivers/block/zram/zram_drv.h
index 5b0afde729cd..e0f725c87cc6 100644
--- a/drivers/block/zram/zram_drv.h
+++ b/drivers/block/zram/zram_drv.h
@@ -84,7 +84,7 @@ struct zram_stats {
         atomic64_t compr_data_size;     /* compressed size of pages stored */
         atomic64_t num_reads;   /* failed + successful */
         atomic64_t num_writes;  /* --do-- */
-        atomic64_t failed_reads;        /* should NEVER! happen */
+        atomic64_t failed_reads;        /* can happen when memory is too low */
         atomic64_t failed_writes;       /* can happen when memory is too low */
         atomic64_t invalid_io;  /* non-page-aligned I/O requests */
         atomic64_t notify_free; /* no. of swap slot free notifications */